The present invention relates to an airbag apparatus.
Airbag apparatuses provided with an airbag having the following configuration have been known. The airbag has a first portion and a second portion, and is folded such that the first portion approaches the second portion. The thus folded airbag has an elongated shape. The airbag has an inlet. When supplied with gas through the inlet, the folded airbag is inflated while being deployed along a predetermined deployment direction, such that the first portion separates from the second portion. The inlet is arranged in a portion of the folded airbag that is located in a trailing side in the deployment direction.
For example, Japanese Laid-Open Patent Publication No. 2004-058849 discloses in paragraphs 0010, 0021 through 0023, and 0029, and FIGS. 3 through 5 a configuration in which a folded airbag having an elongated shape is accommodated between a roof panel and a roof headlining so as to extend in the width of a vehicle. More specifically, the folded airbag is accommodated in a space between rearmost sections of the roof panel and the roof headlining. The roof panel and the roof headlining are bent downward at the rear end of the vehicle, such that the rearmost sections of the roof panel and the roof headlining are substantially parallel to a vertical plane. Attachment portions are provided at an upper portion of the folded airbag. The attachment portions are used to attach the airbag to an inner panel. The inner panel is arranged between the roof panel and the roof headlining and is bent accordingly. In the airbag apparatus disclosed in Japanese Laid-Open Patent Publication No. 2004-058849, gas is supplied from above to the folded airbag, which inflates the airbag while deploying the airbag downward. When deployed and inflated, the airbag intervenes between the rear seats and the rear window.
When the airbag is supplied with gas so that it is deployed and inflated, the momentum of the supplied gas applies a downward urging force, or a force in the deployment direction, to the airbag. However, the airbag is prevented from being displaced downward by the urging force since the airbag is attached to the inner panel at the attachment portions. Further, a tension applying portion extends downward from each end of the folded airbag. The tension applying portions apply outward tension along the width of the vehicle to the airbag. This allows the airbag to be deployed and inflated in a favorable manner from the folded state.
In recent years, to meet the demands for larger spaces of passenger compartments, it has become difficult to secure a space for accommodating a folded airbag in a vehicle rear portion. Therefore, it has become necessary to accommodate a folded airbag in a part closer to the front side of the vehicle, in other words, between sections of the roof panel and the roof headlining that are substantially parallel to the horizontal plane, or in the ceiling of the vehicle. In such a case, an airbag is attached to the inner panel from below. When supplied with gas, an airbag accommodated in the ceiling of a vehicle is inflated while being deployed rearward and downward in the vehicle, so as to intervene between the rear seats and the rear window.
However, in the case where an airbag is accommodated in the ceiling of a vehicle, the desirable deployment and inflation of the airbag are likely to be hindered for the following reasons [1] and [2].
[1] Since the folded airbag is attached to the inner panel from below, the ends of the folded airbag might hang down because of the tension applying portions. When gas is supplied to the airbag in this state, the airbag is inflated while being deployed along an unexpected path.
[2] In the initial stage of the deployment and inflation of the airbag, the airbag receives an urging force due to its own inflation, which urging force acts to pivot the airbag about the attachment portions in a certain direction (for example, forward). If the airbag is pivoted by the urging force, the airbag is inflated while being deployed along an unexpected path.
The above problem that desirable deployment and inflation of an airbag accommodated in the ceiling of a vehicle might be hindered is not unique to airbag apparatuses in which an airbag accommodated in the vehicle ceiling is inflated while being deployed rearward and downward in the vehicle. However, the problem is also found in airbag apparatuses in which an airbag accommodated in the vehicle ceiling is inflated while being deployed outward along the direction of the width of the vehicle.